Function setup 

pub fn setup<H>(
    cs: ConstraintSystem,
    log_inv_rate: usize,
    key_collection: Option<KeyCollection>,
) -> Result<(Verifier<H>, Prover<OptimalPackedB128, H>)>
where
    H: ParallelHashSuite + Clone,
    Output<H::LeafHash>: SerializeBytes + DeserializeBytes,

Set up a non-ZK prover and verifier for the given constraint system using H as the Merkle hash suite.

Providing key_collection skips the expensive key-collection building phase during prover setup.